1. Field of the Invention
The present invention relates to a liquid ejection head mounted on a liquid ejecting device performing a print operation by ejecting a printing liquid such as ink and a manufacturing method of a liquid ejection head.
2. Description of the Related Art
Japanese Patent Laid-Open No. 2002-19146 discloses a liquid ejection head in which a joint seal member is sandwiched between a channel unit formed with a liquid supply path and a support member supporting a printing element substrate and they are press-contacted with each other by a screw to be joined so that the liquid may not leak. The printing element substrate is formed of a silicon (Si) wafer, and a material of the support member uses alumina, e.g., having a linear expansion coefficient equal to that of the printing element substrate.
By making the linear expansion coefficients of the printing element substrate and the support member equal, a stress applied on an adhesive interface between the printing element substrate and the support member caused by a temperature change can be relaxed, and a concern that the printing element substrate is peeled off the support member can be suppressed. Moreover, by sandwiching an elastic member between the channel unit for supplying the liquid to the support member and the support member and screwing and fixing them, ink leak between the channel unit and the support member is prevented, while a manufacturing process is facilitated, and a cost for manufacture is reduced.
However, ink such as ink improved for business which has overcome weak points of the ink having been used in the past such as water resistance or marker resistance has been developed in recent years. With that trend, viscosity of the ink has become high. In order to eject high-viscous ink, it is usually necessary to warm the ink so as to lower the viscosity, but with the support member using alumina, the warmed ink easily cools, and it has been difficult to make the temperature of the ink highly stable before ejection in advance. That is, with the conventional liquid ejection head using alumina for the support member, ink that can be selected is limited. Thus, by changing the material of the support member from alumina which has been used conventionally to a resin, improvement of heat-retaining performance of the printing element substrate can be considered.
Moreover, the printing element substrate of the liquid ejection head has an ejection port forming member for forming an ejection port and a liquid channel for leading a liquid to the ejection port on the substrate on which the printing element is disposed. The ejection port forming member uses an epoxy material as its main material, and it is formed by being patterned on the substrate. In a patterning process, the epoxy material is cured by high-temperature cure. Since the epoxy material with the linear expansion coefficient of approximately 50 ppm/° C. is cured on the Si substrate with the linear expansion coefficient of approximately 7 ppm/° C. at a high temperature, the stress in a direction in which the epoxy material is contracted remains on the Si substrate at a normal temperature after curing.
In a case where the Si substrate with the stress remaining is mounted on the support member formed of a resin, there is a concern as follows. That is, due to a synergic effect of the residual stress of the Si substrate and expansion and contraction of each of the Si substrate and the support member caused by a temperature change in use of the liquid ejection head based on a difference in the linear expansion coefficient between them, the Si substrate might be cracked or the ejection port forming member might be peeled off the Si substrate. Particularly, since the printing element substrate becomes elongated or narrowed in high density, a concern over the crack of the Si substrate or peeling-off of the ejection port forming member grows.